1. Field of the Invention
The present invention relates to a system for converting a test program for a semiconductor integrated circuit.
2. Background Art
To test an LSI (large-scale integrated circuit), first, the LSI to be tested is set on a DUT (device under test) board and the DUT board is set on a pin electronics unit of a tester. The tester judges whether the LSI functions normally by applying a test signal having a prescribed waveform to the LSI and checking a response signal from the LSI. The tester is equipped with a memory for storing programs and an operation device for executing those programs. A test program that is provided in the tester controls or performs signal transmission and reception and check processing.
In this configuration, the transmission line characteristics from the LSI to the tester influence test results. Therefore, after replacement of the tester or the test board, the same test results as before the replacement can no longer be obtained for the same LSI even if the same test program is used.
Conventionally, to replace the tester, deviations in signal timing that are caused by replacement of the tester are observed with an oscilloscope and the test program is modified or the test board is remade so that the deviations are corrected for.
However, adjustment based on observation results is cumbersome and takes time. Further, there is fear that the quality of a test program may lower if the level of the observation skill of an operator is low.
An object of the invention is therefore to provide a method for reducing the load of work of replacing a tester and making it possible to always obtain test programs that are uniform in quality.
Another object of the invention is to provide a program conversion system in which a process according to the above method is executed automatically.
First, a circuit simulator performs simulations for test environments before and after replacement of a tester. That is, the circuit simulator simulates a transmission line characteristic from a semiconductor integrated circuit that is assumed to be mounted on a test board to a tester that is assumed to be connected to the test board based on chip parameters indicating a circuit characteristic of the semiconductor integrated circuit, test board parameters indicating a circuit characteristic of the test board, and tester parameters indicating a circuit characteristic of the tester.
Then, difference acquiring means calculates a difference between transmission characteristics of the two test environments based on simulation results of the circuit simulator, that is, a difference between a transmission characteristic from the semiconductor integrated circuit to a first tester and a transmission characteristic from the semiconductor integrated circuit to a second tester.
Then, program converting means converts a first test program that was generated so as to conform to a first test board and the first tester into a second test program for a second test board and the second tester based on the calculated difference.
The invention also provides a test board designing system which is equipped with the same circuit simulator and the difference acquiring means. The test board designing system is further equipped with, in place of the program converting means, test board parameters determining means for determining test board parameters indicating a new circuit characteristic of the second test board so that the difference calculated by the difference acquiring means becomes equal to zero. That is, the test board designing system assists production of a test board suitable for a second test environment by providing parameters necessary to design the test board.
Other and further objects, features and advantages of the invention will appear more fully from the following description.